Field of the Invention
The present invention relates to a squeeze film damper bearing device having an inner race that is fitted around an outer periphery of a rotating shaft, an outer race that is supported on an inner periphery of a bearing retaining member via an annular space forming a squeeze film, and a plurality of rolling bodies that are disposed between the inner race and the outer race.
Description of the Related Art
Such a squeeze film damper bearing device has the problem that there is a restriction on the oil film thickness of a squeeze film that can give an effective vibration attenuation effect, and when a rotating shaft moves in the radial direction in response to a large vibrational load being inputted and the oil film thickness of the squeeze film becomes too small, the oil film will break, and it will not be possible to obtain an effective vibration attenuation effect. Furthermore, if a large oil film thickness is set in advance for the squeeze film in order to prevent the oil film from breaking, not only will it be impossible to obtain an effective vibration attenuation effect, but there is also the problem that the rotating shaft will become curved due to vibration and will undergo centrifugal whirling.
Therefore, Japanese Patent Application Laid-open No. 8-261231 has made known an arrangement in which a pair of annular concentric springs (oil film break preventing members) are disposed between a bearing metal and a bearing casing, and a constant oil film thickness is maintained for a squeeze film formed between the bearing metal and the bearing casing, thus preventing the oil film of the squeeze film from breaking.
However, in the above conventional arrangement, since the inner periphery and the outer periphery of the concentric springs (oil film break preventing members) always abut against the outer periphery of the rotating shaft and the inner periphery of the bearing casing, not only does the frictional resistance increase and the durability deteriorate, but there is also the problem that a damping effect of the squeeze film cannot be exhibited effectively due to the frictional resistance and, moreover, there is the problem that the number of components and the number of assembly steps increase in proportion to provision of the concentric springs.